The present invention relates generally to an apparatus for forming concrete blocks, and more particularly to a vibrating apparatus for forming a concrete block in a mode of vibration compaction.
A conventional vibrating apparatus has a platform which is elevated in the vertical direction by means of a hydraulic cylinder or the like. The platform has a resilient layer made of resilient material such as rubber on the upper surface thereof. The resilient layer is fixed to the platform. A receiving plate which receives a concrete block to be formed is positioned on the resilient layer of the platform. On the plate is disposed a mold box which has a vibrating device which generally comprises eccentric weights, shafts and devices for driving or rotating the shafts, thereby causing a vibration of the mold box.
In the conventional vibrating apparatus described above, the hydraulic cylinder or the like is driven at first to elevate the platform to thereby secure the receiving plate and the mold box in position. After the plate as well as the mold box is secured in position, concrete material is fed to the mold box by a suitable feeding device. While the concrete material is being fed to the mold box, the vibrating device is driven to vibrate the mold box in the vertical direction to thereby accomplish vibration compaction. After the concrete material is fully fed to the mold box, the vibrating device is continuously driven, and at the same time a compression molding press, which is installed above the mold box and has a plate, is driven to lower the plate to compression-mold a concrete block. After the compression molding is completed, the plate of the compression molding press and the receiving plate are lowered with the distance therebetween being maintained. Namely, the plate of the compression molding press and the platform connected to the hydraulic cylinder or the like are simultaneously lowered at the same speed. In this instance, the mold box abuts against, and is received by, shoulders which are disposed below the mold box. Thus, the mold box stops at the predetermined position and is not lowered any further. While the mold box is received by the shoulders so that the same is not lowered any further, the compression molding press and the hydraulic cylinder or the like are continuously driven to lower further the molded concrete block, receiving plate and the platform. Thus, the concrete block is removed from the mold box and is then delivered to a predetermined position.
The above described conventional vibration device aims to allow a vibration from the mold box to the concrete material by way of the receiving plate. Here, it is considered that compaction effect of the material is proportional to a vibration accleration of the mold box
However, the conventional vibration device has serious disadvantages in that (a) a filling or packing density is not desirably high and filling time is long because the vibration of the mold box is decreasingly transmitted to the materials for a concrete block within the mold box; (b) a great noise is produced due to a successive abutment and separation between the mold box and the receiving plate; and (c) the resulting products are poor in finish particularly bottom edges thereof. The inventor has found that these disadvantages are due to the fact that the receiving plate cannot follow the vibration of the mold box because a vibration acceleration of the mold box exceeds, in general, a vibration accleration of the receiving plate, the latter being produced by the resilient force of the resilient layer of the platform.
The above-described disadvantages are unavoidable with respect to the conventional device, and are more conspicuous when the apparatus becomes larger. Namely, as weight of the receiving plate becomes greater, it becomes further difficult to obtain a close contact between the receiving plate and the mold box, and this difficulty results in disadvantages as described above.